The long-term objective of this proposal is to investigate the molecular basis of cerebrovascular endothelial cell damage as a result of hypertensive injury. Actue hypertension can evoke cerebrovascular endothelial abnormalities including breach of the blood-brain barrier and consequent brain edema. The (Na+ + K+)- ATPase, present in cerebroendothelium, may contribute to sodium balance and, if compromised, to brain edema. Use of isolated capillaries derived from cerebral cortex permits examination of intraparenchymal vessels in a well-controlled in vitro environment whereby mechanisms of blood-brain barrier function may be directly evaluated. Thus, the specific aim of this proposal is to examine the regulation of the cerebromicrovascular (Na+ + K+)- ATPase in vitro by arachidonic acid, a substance implicated in hypertensive injury, and catecholamines, possible regulators of blood-brain barrier permeability. In addition, combinations of arachidonic acid catecholamines will be evaluated for synergistic or antagonistic effects on (Na+ + K+)- and ATPase activity. Furthermore, microvessels derived from animals infused with angiotensin amide to evoke acute hypertension will be used to determine if the basal cerebrovascular (Na+ + K+)-ATPase is affected and if this enzyme shows an altered response to arachidonic acid and/or catecholamines. The activity of the cerebrovascular (Na+ + K+)-ATPase will be measured by: a) (3H)-ouabain binding; b) inorganic phosphate release; and c) rubidium uptake and efflux. Data derived from these experiments will help to delineate which functions of the enzyme are susceptible to regulation by arachidonic acid and/or catecholamines. Results of this study may indicate how the cerebromicrovascular (Na+ + K+)-ATPase is regulated by substances which are implicated in hypertension and if this regulation is altered after acute hypertensive injury. An understanding of the molecular mechanisms that underlie blood-brain barrier ionic perturbation in hypertension may eventually suggest therapeutic modalities for intervention in these processes.